Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$69.35	3.127%	$71.5186	$71.52	$71.50	$71.50
Purchase #2	$9.74	11.818%	$10.8911	$10.89	$10.90	$10.90
Purchase #3	$146.91	10.448%	$162.2592	$162.26	$162.25	$162.30
Purchase #4	$151.28	9.158%	$165.1342	$165.13	$165.15	$165.10
Purchase #5	$173.52	4.830%	$181.901	$181.90	$181.90	$181.90
Purchase #6	$185.72	13.595%	$210.9686	$210.97	$210.95	$211.00
Purchase #7	$41.59	13.176%	$47.0699	$47.07	$47.05	$47.10
7 purchase totals =	$778.11		$849.7426	$849.74	$849.70	$849.80